Method for controlling the shift invariance of optical correlators

Michael Levene, Gregory J. Steckman, and Demetri Psaltis

Michael Levene, Gregory J. Steckman, and Demetri Psaltis

When this research was performed, M. Levene was with Computation and Neural Systems and G. J. Steckman (steckman@caltech.edu) and D. Psaltis were with the Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125.

M. Levene is now with the Department of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853.

Abstract

Holographic correlators can implement many correlations in
parallel. For most systems shift invariance limits the number of
correlation templates that can be stored in one correlator. This is
because the output plane must be divided among the individual templates
in the system. When the system is completely shift invariant, the
correlation peak from one correlator can shift into an area that has
been reserved for a different template; in this case a shifted version
of one object might be mistaken for a well-centered version of a
different object. We describe a technique for controlling the shift
invariance of a correlator system by moving the holographic material
away from the Fourier plane.